The principle of thermos bottle is simple: the bottle has an inner wall and an outer wall; There is a vacuum between the two walls. Heat conduction and convection cannot be carried out in vacuum, but the metal-plated reflective layer can reflect thermal radiation. Therefore, any liquid poured into the bottle can keep its original temperature for a long time.
This is why thermos bottles can keep warm in winter and cool down in summer. Many people who have traveled many times find it hard to imagine what it would be like without a thermos. Dewar bottles produce liquid oxygen at a low temperature of MINUS 240 degrees Celsius. In order to preserve this liquid oxygen, he designed a bottle in which heat can't go in or out. The thermos bottle we use evolved from this kind of "Dewar bottle". Dewar's thermos bottle is designed according to heat transfer: first, it is made of two layers of glass bottles, and vacuum is pumped in the middle of the bottle to isolate the heat conduction and convection of air; Second, the bottle wall is plated with silver, just like a mirror reflecting light, which can reflect thermal radiation back into the bottle; Third, the bottle mouth is covered with a cork to prevent heat from slipping out of the bottle mouth. If it is used to hold boiling water, it becomes a thermos. However, it was the German glass manufacturer Reinhold Berg who realized that thermos bottles would be useful in various situations. He obtained the patent of thermos bottle in 1903 and made a plan to put it on the market. Berg even held a contest to name his thermos. The award-winning name he chose was "Thermos", which means heat in Greek.
Berg's products were very successful, and soon he shipped thermos bottles all over the world. Hot water bottles are usually used for scientific purposes, for example, when the liquid needs to be kept at a constant temperature. Vaccinia, serum and other liquids are often transported in thermos bottles. The inside of the thermos bottle is no longer coated with mercury. Before the 1960s, it was coated with silver and magnesium oxide.
Classification and use
Thermos can be divided into three categories: ① Fine-mouthed type. Also known as thermos. Small caliber, good thermal insulation performance, mainly used for boiling hot water, fried Chinese medicine juice, hot drinks and cold drinks. ② Big mouth type. Also called ice bottle. The diameter of the mouth is large, so it is convenient to take and put things. It mainly includes ice cubes, sorbets, cold drinks with containers, iced drugs, liquefied gas, anti-fermentation substances and so on. You can also use containers for hot food and hot drinks. 3 cups. It is usually called a thermos cup. Large caliber, small capacity, mainly used as tableware, can reduce the impact of environmental temperature on the contents in a short time.